Current events, e.g., the discovery of toxins in toys, environmental air and water concerns, and resulting regulations dictate an urgent need for an analyzer for toxic element determination. Advanced x-ray fluorescence (XRF) analyzers can play a valuable role in the quantification of such toxins and many other substances of interest in a variety of samples, e.g., toxins in consumer products, and various harmful elements in petroleum products.
As one prominent example, manufacturers, suppliers, distributors, retailers, and regulatory entities need a long-term solution for toxic-element analysis for a wide variety of consumer goods. Many new regulations require manufacturers to detect many elements such as lead (Pb), mercury (Hg), arsenic (As), cadmium (Cd), chromium (Cr), bromine (Br), selenium (Se), antimony (Sb), barium (Ba), and chlorine (Cl). In the EU regulations, the maximum concentration in a homogenous material is 1,000 ppm for hexavalent chromium (Cr6+), Hg, Pb, polybrominated biphenyl (PBB), and polybrominated diphenyl ethers (PBDE), and 100 ppm for Cd. The new U.S. regulation (CPSIA) for children's products is much more restrictive. For example, the maximum allowable lead level in toys and children's jewelry is less than or equal to 100 ppm in any accessible part of a product.
Current measurement methods are either accurate enough but not usable on the factory floor, or they may be convenient for use on the factory floor but not close to being sufficiently sensitive or repeatable. As a result, there is a need for a truly fit-for-purpose analyzer for this application.
More generally, there is a strong market need for a rapid, reliable, convenient, nondestructive, high-sensitivity, quantitative, cost-effective analyzer to carry out critical and conclusive measurements with a single instrument in a manufacturing facility either at-line or on-line, or any place in a distribution chain. Contaminated products can be eliminated at the most advantageous place in the process, substantially mitigating or even eliminating accidental production waste and errors. There is also a strong need for a similar capability at several stages in the distribution and by regulators to verify the compliance of materials and products.
In x-ray analysis systems, high x-ray beam intensity and small beam spot sizes are important to reduce sample exposure times, increase spatial resolution, and consequently, improve the signal-to-background ratio and overall quality of x-ray analysis measurements. In the past, expensive and powerful x-ray sources in the laboratory, such as rotating anode x-ray tubes or synchrotrons, were the only options available to produce high-intensity x-ray beams. Recently, the development of x-ray optics enables collection of the diverging radiation from an x-ray source by focusing the x-rays. A combination of x-ray focusing optics and small, low-power x-ray sources can produce x-ray beams with intensities comparable to those achieved with larger, high-power, and more expensive devices. As a result, systems based on a combination of small, inexpensive x-ray sources, excitation optics, and collection optics are greatly expanding the availability and capabilities of x-ray analysis equipment in, for example, small laboratories and in the field, factory, or clinic, etc.
Monochromatization of x-ray beams in the excitation and/or detection paths is also useful to excite and/or detect very precise portions of the x-ray energy spectrum corresponding to various elements of interest (lead, etc.). X-ray monochromatization technology is based on diffraction of x-rays on optical crystals, for example, germanium (Ge) or silicon (Si) crystals. Curved crystals can provide deflection of diverging radiation from an x-ray source onto a target, as well as providing monochromatization of photons reaching the target. Two common types of curved crystals are known as singly-curved crystals and doubly-curved crystals (DCCs). Using what is known in the art as Rowland circle geometry, singly-curved crystals provide focusing in two dimensions, leaving x-ray radiation unfocused in the third or orthogonal plane. Doubly-curved crystals provide focusing of x-rays from the source to a point target in all three dimensions. This three-dimensional focusing is referred to in the art as “point-to-point” focusing.
The present invention addresses challenges presented in the fabrication and mounting of such monochromating optics in new x-ray analysis systems, in which performance and alignment improvements are continually needed, along with decreases in size, weight, power and cost.